The molecular structure of human procollagen will be studied by physical and chemical methodologies. In vitro culture methods utilizing cloned human fibroblasts will be employed under conditions limiting proteolytic degradation of procollagen. Specific areas to be investigated include the elucidation of the single versus multiple chain models for procollagen I, the molecular basis for biological chain registration, and a probe for the possible role of procollagen as a precursor for other collagen-like structural proteins.